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Temperature dependence of electrochemical degradation in LiNi 1/3 Mn 1/3 Co 1/3 O 2 /Li 4 Ti 5 O 12 cells

DOI: 10.1002/ente.201900310 DOI Help

Authors: Erik Bjorklund (Uppsala University) , Andrew J. Naylor (Uppsala University) , William Brant (Uppsala University) , Daniel Brandell (Uppsala University) , Reza Younesi (Uppsala University) , Kristina Edström (Uppsala University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Energy Technology

State: Published (Approved)
Published: May 2019
Diamond Proposal Number(s): 18974

Abstract: Ageing mechanisms in Li‐ion batteries are dependent on the operational temperature but the detailed mechanisms on what processes that takes place at what temperature is still lacking. The electrochemical performance and capacity fading of the common cell chemistry LiNi1/3Mn1/3Co1/3O2 (NMC)/Li4Ti5O12 (LTO) pouch cells is studied at the temperatures: −10 °C, 30 °C and 55 °C. The full cells are cycled with the moderate upper cut‐off potential: 4.3 V vs. Li+/Li. The electrode interfaces are characterized post‐mortem using photoelectron spectroscopy techniques (SOXPES, HAXPES, XANES). Stable cycling at 30 °C is explained by electrolyte reduction forming a stabilizing interphase, thereby preventing further degradation. This initial reaction, between LTO and the electrolyte, seems to be beneficial for the NMC‐LTO full cell. At 55 °C, continuous electrolyte reduction and capacity fading is observed. It leads to formation of a thicker surface layer of organic‐species on the LTO surface than at 30 °C, contributing to an increased voltage hysteresis. At −10 °C, large cell‐resistances are observed, caused by poor electrolyte conductivity in combination with a relatively thicker and LixPFy‐rich surface layer on LTO, which all limit the capacity. ‘Slippage’ with a reduced voltage window showing the loss of active Li+ was observed using XRD.

Journal Keywords: Li‐ion battery; Ageing; Photoelectron spectroscopy

Subject Areas: Chemistry, Energy


Instruments: I09-Surface and Interface Structural Analysis